1. Field of the Invention
The present invention relates to a handheld tool which is provided in particular for dental purposes and is designed to dispense a pasty filling material, the viscosity of which can be reduced by supplying oscillation energy. Furthermore, the present invention relates to a container for accommodating a pasty filling material, which can be used in such a handheld tool.
2. Related Technology
In medical technology, it is known to fill, and thus to repair, cavities in an animal or human body part or in a prosthesis with a filling material, for example after a defect has been eliminated by removal of material. For this purpose, use is made of curable filling materials, which are introduced into the cavity in a pasty or liquid state and then cure. In this case, a distinction should be made between a direct filling and an indirect filling. In a direct filling, only the filling material is introduced into the cavity so that it fills the cavity. In an indirect filling, a preferably matching inlay insert containing the filling material is inserted into the cavity so that the inlay insert connects the insert to the wall of the cavity. In this case, not only mechanical anchoring of the filling material in the cavity is important, but also sealed accommodation of the filling material in the cavity, in order to avoid gaps which can be passed through by contamination and germs, which can lead to inflammation in a body tissue and can destroy the preparation.
A typical application of an above-described preparation, in which there are particular requirements with regard to the handheld tool and the handling thereof, is tooth preparation in the oral cavity of a patient or in a practice head for learning purposes. In such a dental treatment case, there are particular requirements with regard to the structural size of the handpiece, since the oral cavity of a patient is comparatively small and therefore, with necessary visibility being taken into account, a structural size which is as small as possible should be sought.
DE 100 01 513 A1 describes a method for filling a synthetic resin-based tooth filling material into a cavity of a tooth and a handheld tool for carrying out such a method, wherein, during filling, the filling material and a nozzle of the handheld tool are acted on with sound, in particular with ultrasound, and the handheld tool has means which convey the filling material out of a storage container in the nozzle. This known method and handheld tool make it possible to use filling materials having a comparatively high content of fillers, which increase the viscosity of the filling material and thus reduce shrinkage and the risk of gaps forming during curing. In this previously known handheld tool, there is provided a lever device for conveying the filling material, and when this lever device is manually actuated an ultrasound source, in particular a piezoelectric oscillator, is switched on at the same time, this ultrasound source or piezoelectric oscillator being arranged in the rear region of the body of the handheld tool. The filling material is arranged in a cartridge, which can be inserted into a cutout arranged in the front end region of the body of the handheld tool and fixed therein. When the lever device is manually actuated, the filling material is conveyed out by a feed ram which is connected to the lever device and acts on the rear end of the cartridge.
A comparable tool is also known from WO 2006/13639 A2 of the applicant. In this case, particular modifications to the handheld tool are proposed, which help to improve both the dispensing of the composite material and also the handling of the tool.
For reasons of hygiene, it would be advantageous to configure the storage container for the composite material with the outlet nozzle in the form of a cartridge, as a disposable or single-use article. For each treatment, a new cartridge could then be used, so that cleaning and disinfection, which would otherwise be essential, can be avoided. On the other hand, the result of this solution is that a detachable connection is necessary between the storage container and the handheld tool, and this can lead to problems with regard to the effectiveness of oscillation transmission and with the dispensing of the filling material.